Set up

library(tidyverse)
library(tidyquant) # for financial analysis
library(broom) # for tidy model results
library(umap)  # for dimension reduction
library(plotly) # for interactive visualization

Data

# Get info on companies listed in S&P500
sp500_index_tbl <- tq_index("SP500")

# Get individual stocks from S&P500
sp500_symbols <- sp500_index_tbl %>% distinct(symbol) %>% pull() 

# Get stock prices of the companies
sp500_prices_tbl <- tq_get(sp500_symbols, from = "2020-04-01")

write.csv(sp500_index_tbl, "../00_data/sp500_index_tbl.csv")
write.csv(sp500_prices_tbl, "../00_data/sp500_prices_tbl.csv")

Import data

sp500_index_tbl <- read_csv("../00_data/sp500_index_tbl.csv")
sp500_prices_tbl <- read_csv("../00_data/sp500_prices_tbl.csv")
sp500_index_tbl %>% glimpse()
## Rows: 504
## Columns: 9
## $ ...1           <dbl> 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, …
## $ symbol         <chr> "AAPL", "MSFT", "NVDA", "AMZN", "META", "BRK-B", "GOOGL…
## $ company        <chr> "APPLE INC", "MICROSOFT CORP", "NVIDIA CORP", "AMAZON.C…
## $ identifier     <chr> "037833100", "594918104", "67066G104", "023135106", "30…
## $ sedol          <chr> "2046251", "2588173", "2379504", "2000019", "B7TL820", …
## $ weight         <dbl> 0.063852496, 0.063282113, 0.058805166, 0.038154398, 0.0…
## $ sector         <chr> "-", "-", "-", "-", "-", "-", "-", "-", "-", "-", "-", …
## $ shares_held    <dbl> 185532921, 91814848, 302468387, 116491471, 27046746, 22…
## $ local_currency <chr> "USD", "USD", "USD", "USD", "USD", "USD", "USD", "USD",…
sp500_prices_tbl %>% glimpse()
## Rows: 629,218
## Columns: 9
## $ ...1     <dbl> 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18…
## $ symbol   <chr> "AAPL", "AAPL", "AAPL", "AAPL", "AAPL", "AAPL", "AAPL", "AAPL…
## $ date     <date> 2020-04-01, 2020-04-02, 2020-04-03, 2020-04-06, 2020-04-07, …
## $ open     <dbl> 61.6250, 60.0850, 60.7000, 62.7250, 67.7000, 65.6850, 67.1750…
## $ high     <dbl> 62.1800, 61.2875, 61.4250, 65.7775, 67.9250, 66.8425, 67.5175…
## $ low      <dbl> 59.7825, 59.2250, 59.7425, 62.3450, 64.7500, 65.3075, 66.1750…
## $ close    <dbl> 60.2275, 61.2325, 60.3525, 65.6175, 64.8575, 66.5175, 66.9975…
## $ volume   <dbl> 176218400, 165934000, 129880000, 201820400, 202887200, 168895…
## $ adjusted <dbl> 58.46381, 59.43937, 58.58514, 63.69596, 62.95821, 64.56961, 6…

Question

Which stock prices behave similarly?

Our main objective is to identify stocks that exhibit similar price behaviors over time. By doing so, we aim to gain insights into the relationships between different companies, uncovering potential competitors and sector affiliations.

Why It Matters Understanding which companies are related is crucial for various reasons:

Assignment Details Your task is to analyze the historical price data of various stocks and determine which stocks behave similarly. We will employ clustering techniques to accomplish this task effectively.

1 Convert data to standardized form

To compare data effectively, it must be standardized or normalized. Why? Because comparing values (like stock prices) of vastly different magnitudes is impractical. So, we’ll standardize by converting from adjusted stock price (in dollars) to daily returns (as percent change from the previous day). Here’s the formula:

\[ return_{daily} = \frac{price_{i}-price_{i-1}}{price_{i-1}} \]

sp500_prices_tbl %>% glimpse()
## Rows: 629,218
## Columns: 9
## $ ...1     <dbl> 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18…
## $ symbol   <chr> "AAPL", "AAPL", "AAPL", "AAPL", "AAPL", "AAPL", "AAPL", "AAPL…
## $ date     <date> 2020-04-01, 2020-04-02, 2020-04-03, 2020-04-06, 2020-04-07, …
## $ open     <dbl> 61.6250, 60.0850, 60.7000, 62.7250, 67.7000, 65.6850, 67.1750…
## $ high     <dbl> 62.1800, 61.2875, 61.4250, 65.7775, 67.9250, 66.8425, 67.5175…
## $ low      <dbl> 59.7825, 59.2250, 59.7425, 62.3450, 64.7500, 65.3075, 66.1750…
## $ close    <dbl> 60.2275, 61.2325, 60.3525, 65.6175, 64.8575, 66.5175, 66.9975…
## $ volume   <dbl> 176218400, 165934000, 129880000, 201820400, 202887200, 168895…
## $ adjusted <dbl> 58.46381, 59.43937, 58.58514, 63.69596, 62.95821, 64.56961, 6…
# Apply your data transformation skills!
sp_500_daily_returns_tbl <- sp500_prices_tbl %>%
    
    select(symbol, date, adjusted) %>%
    
    filter(date >= ymd("2018-01-01")) %>%
    
    group_by(symbol) %>%
    mutate(lag_1 = lag(adjusted)) %>%
    ungroup() %>%
    
    filter(!is.na(lag_1)) %>%
    
    mutate(diff = adjusted - lag_1) %>%
    mutate(pct_return = diff / lag_1) %>%
    
    select(symbol, date, pct_return)

sp_500_daily_returns_tbl
## # A tibble: 628,715 × 3
##    symbol date       pct_return
##    <chr>  <date>          <dbl>
##  1 AAPL   2020-04-02    0.0167 
##  2 AAPL   2020-04-03   -0.0144 
##  3 AAPL   2020-04-06    0.0872 
##  4 AAPL   2020-04-07   -0.0116 
##  5 AAPL   2020-04-08    0.0256 
##  6 AAPL   2020-04-09    0.00722
##  7 AAPL   2020-04-13    0.0196 
##  8 AAPL   2020-04-14    0.0505 
##  9 AAPL   2020-04-15   -0.00913
## 10 AAPL   2020-04-16    0.00795
## # ℹ 628,705 more rows

2 Spread to object-characteristics format

We’ll convert the daily returns (percentage change from one day to the next) to object-characteristics format, also known as the user-item format. Users are identified by the symbol (company), and items are represented by the pct_return at each date.

stock_date_matrix_tbl <- sp_500_daily_returns_tbl %>%
    spread(key = date, value = pct_return, fill = 0)

stock_date_matrix_tbl
## # A tibble: 503 × 1,264
##    symbol `2020-04-02` `2020-04-03` `2020-04-06` `2020-04-07` `2020-04-08`
##    <chr>         <dbl>        <dbl>        <dbl>        <dbl>        <dbl>
##  1 A           0.0489     -0.0259         0.0560     -0.00444       0.0359
##  2 AAPL        0.0167     -0.0144         0.0872     -0.0116        0.0256
##  3 ABBV        0.0233     -0.0234         0.0322     -0.00449       0.0420
##  4 ABNB        0           0              0           0             0     
##  5 ABT         0.0375      0.000126       0.0413     -0.00967       0.0369
##  6 ACGL        0.0115     -0.0650         0.0983      0.0314        0.0291
##  7 ACN         0.0103     -0.0264         0.0914     -0.0116        0.0464
##  8 ADBE        0.00913    -0.0341         0.0869     -0.0320        0.0267
##  9 ADI         0.0429     -0.0130         0.107       0.00470       0.0535
## 10 ADM         0.0136      0.00932        0.0326      0.00559       0.0139
## # ℹ 493 more rows
## # ℹ 1,258 more variables: `2020-04-09` <dbl>, `2020-04-13` <dbl>,
## #   `2020-04-14` <dbl>, `2020-04-15` <dbl>, `2020-04-16` <dbl>,
## #   `2020-04-17` <dbl>, `2020-04-20` <dbl>, `2020-04-21` <dbl>,
## #   `2020-04-22` <dbl>, `2020-04-23` <dbl>, `2020-04-24` <dbl>,
## #   `2020-04-27` <dbl>, `2020-04-28` <dbl>, `2020-04-29` <dbl>,
## #   `2020-04-30` <dbl>, `2020-05-01` <dbl>, `2020-05-04` <dbl>, …

3 Perform k-means cluster

stock_cluster <- kmeans(stock_date_matrix_tbl %>%
select(-symbol), centers = 5, nstart = 20)
summary(stock_cluster)
##              Length Class  Mode   
## cluster       503   -none- numeric
## centers      6315   -none- numeric
## totss           1   -none- numeric
## withinss        5   -none- numeric
## tot.withinss    1   -none- numeric
## betweenss       1   -none- numeric
## size            5   -none- numeric
## iter            1   -none- numeric
## ifault          1   -none- numeric
tidy(stock_cluster)
## # A tibble: 5 × 1,266
##   `2020-04-02` `2020-04-03` `2020-04-06` `2020-04-07` `2020-04-08` `2020-04-09`
##          <dbl>        <dbl>        <dbl>        <dbl>        <dbl>        <dbl>
## 1      0.00620      -0.0196       0.0857      0.0129        0.0466      0.0273 
## 2      0.0122       -0.0185       0.0913     -0.00447       0.0358      0.00646
## 3      0.0867        0.0170       0.0691      0.0345        0.0674      0.0143 
## 4     -0.0167       -0.0262       0.114       0.0396        0.0627      0.0481 
## 5      0.0226       -0.0113       0.0577     -0.00470       0.0350      0.0216 
## # ℹ 1,260 more variables: `2020-04-13` <dbl>, `2020-04-14` <dbl>,
## #   `2020-04-15` <dbl>, `2020-04-16` <dbl>, `2020-04-17` <dbl>,
## #   `2020-04-20` <dbl>, `2020-04-21` <dbl>, `2020-04-22` <dbl>,
## #   `2020-04-23` <dbl>, `2020-04-24` <dbl>, `2020-04-27` <dbl>,
## #   `2020-04-28` <dbl>, `2020-04-29` <dbl>, `2020-04-30` <dbl>,
## #   `2020-05-01` <dbl>, `2020-05-04` <dbl>, `2020-05-05` <dbl>,
## #   `2020-05-06` <dbl>, `2020-05-07` <dbl>, `2020-05-08` <dbl>, …
augment(stock_cluster, stock_date_matrix_tbl) %>%
     ggplot(aes(symbol, `2020-04-02`, color = .cluster)) +
    geom_point()

4 Select Optimal Number of Clusters

kclusts <- tibble(k = 1:9) %>%
    mutate(kclust = map(.x = k, .f = ~ kmeans(stock_date_matrix_tbl %>%
select(-symbol), centers = .x, nstart = 20)),
            glanced = map(.x = kclust, .f = glance))

kclusts %>%
    unnest(glanced) %>%
    ggplot(aes(k, tot.withinss)) +
    geom_point() +
    geom_line()

final_cluster <- kmeans(stock_date_matrix_tbl %>% select(-symbol), centers = 5, nstart = 20)

5 Reduce Dimensions Using UMAP

umap_results <- stock_date_matrix_tbl %>%
    select(-symbol) %>%
    umap()

umap_results_tbl <- umap_results$layout %>%
    as.tibble() %>%
    bind_cols(stock_date_matrix_tbl %>% select(symbol))

umap_results_tbl
## # A tibble: 503 × 3
##        V1      V2 symbol
##     <dbl>   <dbl> <chr> 
##  1  2.67   1.33   A     
##  2  3.04  -0.543  AAPL  
##  3  0.392  2.11   ABBV  
##  4  2.41  -1.21   ABNB  
##  5  1.30   1.72   ABT   
##  6 -1.40  -0.706  ACGL  
##  7  1.86  -0.0822 ACN   
##  8  3.05  -0.473  ADBE  
##  9  2.78  -2.20   ADI   
## 10 -1.27  -0.436  ADM   
## # ℹ 493 more rows
umap_results_tbl %>%
    ggplot(aes(V1, V2)) +
    geom_point()

6 Visualize Clusters by Adding k-means results

kmeans_umap_tbl <- final_cluster %>%
    augment(stock_date_matrix_tbl) %>%
    select(symbol, .cluster) %>%
    
    left_join(umap_results_tbl) %>%
    
    cross_join(sp_500_daily_returns_tbl %>%
                  select(-date) %>%
                  pivot_wider(names_from = symbol, values_from = pct_return) %>%
                  janitor::clean_names())

kmeans_umap_tbl
## # A tibble: 503 × 507
##    symbol .cluster     V1      V2 aapl   msft   nvda   amzn   meta   brk_b googl
##    <chr>  <fct>     <dbl>   <dbl> <list> <list> <list> <list> <list> <lis> <lis>
##  1 A      2         2.67   1.33   <dbl>  <dbl>  <dbl>  <dbl>  <dbl>  <dbl> <dbl>
##  2 AAPL   5         3.04  -0.543  <dbl>  <dbl>  <dbl>  <dbl>  <dbl>  <dbl> <dbl>
##  3 ABBV   1         0.392  2.11   <dbl>  <dbl>  <dbl>  <dbl>  <dbl>  <dbl> <dbl>
##  4 ABNB   5         2.41  -1.21   <dbl>  <dbl>  <dbl>  <dbl>  <dbl>  <dbl> <dbl>
##  5 ABT    1         1.30   1.72   <dbl>  <dbl>  <dbl>  <dbl>  <dbl>  <dbl> <dbl>
##  6 ACGL   2        -1.40  -0.706  <dbl>  <dbl>  <dbl>  <dbl>  <dbl>  <dbl> <dbl>
##  7 ACN    2         1.86  -0.0822 <dbl>  <dbl>  <dbl>  <dbl>  <dbl>  <dbl> <dbl>
##  8 ADBE   5         3.05  -0.473  <dbl>  <dbl>  <dbl>  <dbl>  <dbl>  <dbl> <dbl>
##  9 ADI    5         2.78  -2.20   <dbl>  <dbl>  <dbl>  <dbl>  <dbl>  <dbl> <dbl>
## 10 ADM    2        -1.27  -0.436  <dbl>  <dbl>  <dbl>  <dbl>  <dbl>  <dbl> <dbl>
## # ℹ 493 more rows
## # ℹ 496 more variables: avgo <list>, goog <list>, tsla <list>, jpm <list>,
## #   lly <list>, v <list>, unh <list>, xom <list>, cost <list>, ma <list>,
## #   nflx <list>, wmt <list>, pg <list>, jnj <list>, hd <list>, abbv <list>,
## #   ko <list>, crm <list>, bac <list>, pm <list>, cvx <list>, csco <list>,
## #   mcd <list>, orcl <list>, abt <list>, ibm <list>, wfc <list>, lin <list>,
## #   pep <list>, mrk <list>, ge <list>, t <list>, pltr <list>, vz <list>, …

Help Please!

# g <- kmeans_umap_tbl %>%
    
   #  mutate(text_label = str_glue("Symbol: {symbol}
                                # Cluster: {.cluster}
                                 #Date: {'2020-04-02' %>% scales::percent(1)}")) %>%
    
    # ggplot(aes(V1, V2, color = .cluster, text = text_label)) +
   # geom_point()

# g %>% ggplotly(tooltip = "text")